The present invention relates to a process and apparatus for the continuous production of a welded or seamed filler wire of random length formed from a metal tube and a pulverulent material filling and which is shaped from a metal strip in the form of a split or open joint tube which is open at the top, into which the pulverulent material is introduced during its continuous advance and which, by compression and welding or seaming its longitudinal edges, can be formed into a tube enclosing the material filling. The tube is then reduced to a smaller diameter forming the filler wire.
The production of a filler wire shaped in a continuous production process has long been known. With the installations used for this, it is possible to produce filler wires having a random length and differing construction, as well as for different fields of use. In a known process (EP-A-3,370) the filler wire is produced in the form of a powder-filled tube from a metal strip, the strip firstly being shaped into a channel, into which the powder is introduced and then the channel is shaped into a tube and welded. Contacts mounted on the tube are connected to a high frequency generator. The high frequency current introduced into the tube by the same is concentrated at the longitudinal edges of the channel compressed to form a tube and heats it to welding temperature. After welding, the weld bead formed by the welding process on the tube is levelled and the tube is calibrated or sized, before it is reduced to the final diameter by a drawing operation.
This process and the corresponding installation make it possible to produce filler wires with relatively high running speeds. However, it is a disadvantage that it is not possible to reliably produce a completely satisfactory weld, as is required for a subsequent copper plating of the filler wire.
In another known process (DE-Al-2,515,342) for forming the tubular wire, a metal strip is shaped into a channel and is filled with the pulverulent material to form the core. Simultaneously, a cover strip with a longitudinal fold is placed in the channel, which is shaped to a tube and is welded by means of a welding apparatus at its longitudinal edges. Following welding, the closed tube is reduced to the desired diameter by a drwing process.
The use of the cover strip is intended to prevent particles of pulverulent material being deposited on the longitudinal edges of the tube to be welded, so as to impair the quality of the weld. However, this is only incompletely achieved in the case of the conventional welding speeds, so that here again a reliable weld is not obtained. The unequal material distribution in the tube wall is also disadvantageous so that such a welding rod can bend out during welding.